Designing folding knives

[D. Crawford]

I've been working on my first folder (a slip joint) and was surprised at the work involved in getting the geometry of the blade shape,
tang and back spring just right. To those of you who make folders, how do you go about your design & build process?
Do you use pencil and paper or CAD software? Do you start from scratch every time or reuse your templates & alter them for new designs?
Do you make prototypes to iron out the bugs? I'd like to hear your thoughts. Thanks.

 

[KCorn]

One of the best ways is to buy an old used slip joint of a design you like and take a carpet scraper blade (you can buy them at Home Depot) and place it between the liner and the blade and bang away with a hammer until it cuts through the pivot pin. You can. It the other pins the same way and take the knife completely apart. You now have a pattern to use. It's really pretty easy to do. My best suggestion for ya though is to order the slip joint DVD by Chris Crawford. The DVD comes with a pattern and it will walk you through every step in a very easy to follow method. Hope that helps!

 

[EdCaffreyMS]

In general most of us who produce folders tend to stick with variations on a few differnt patterns. Personally, I like to use thin plexiglass when developing a new folder pattern. I cut out and drill the parts as if I were doing it with steel, but the plexiglass allows me to see through everything, making it easier to figure out the various geometries.

The most important portion of folder design is the "triangle" of pivot, lock, and stop pin when dealing with a liner-lock design. It's essentially the same with slip joints, but persoanally I think they are more difficult because of the "rise/fall" factor of the backspacer/spring. All that being said, once you figure out that "triangle" you can pretty much do whatever you want with the rest of the knife.

Making folders is another "step up" in a knifemakers evolution....I generally tell my students that with straight knives you deal in fractions of an inch......with folders you deal in thousandths of an inch.

 

[Calvin Robinson]

In general most of us who produce folders tend to stick with variations on a few differnt patterns. Personally, I like to use thin plexiglass when developing a new folder pattern. I cut out and drill the parts as if I were doing it with steel, but the plexiglass allows me to see through everything, making it easier to figure out the various geometries.

The most important portion of folder design is the "triangle" of pivot, lock, and stop pin when dealing with a liner-lock design. It's essentially the same with slip joints, but persoanally I think they are more difficult because of the "rise/fall" factor of the backspacer/spring. All that being said, once you figure out that "triangle" you can pretty much do whatever you want with the rest of the knife.

Making folders is another "step up" in a knifemakers evolution....I generally tell my students that with straight knives you deal in fractions of an inch......with folders you deal in thousandths of an inch.

Good advice Ed!

 

[Don Robinson]

I have several CAD designs I print out and use as paper patterns for sawing the basic outlines of the blade, handle and spring.

I've never made a template or a prototype for any knife. Each one is unique.

Yes, getting the rise and fall right is a chore.

 

[D. Crawford]

In general most of us who produce folders tend to stick with variations on a few differnt patterns. Personally, I like to use thin plexiglass when developing a new folder pattern. I cut out and drill the parts as if I were doing it with steel, but the plexiglass allows me to see through everything, making it easier to figure out the various geometries.

The most important portion of folder design is the "triangle" of pivot, lock, and stop pin when dealing with a liner-lock design. It's essentially the same with slip joints, but persoanally I think they are more difficult because of the "rise/fall" factor of the backspacer/spring. All that being said, once you figure out that "triangle" you can pretty much do whatever you want with the rest of the knife.

Making folders is another "step up" in a knifemakers evolution....I generally tell my students that with straight knives you deal in fractions of an inch......with folders you deal in thousandths of an inch.

Thanks for the info Ed, and I'll try the plexiglass. Yep, understanding the "triangle" and its geometry was my main goal while doing this first folding knife. After several years of doing only fixed blades, I'm really looking forward to taking this next step in my progression as a maker.

 

[D. Crawford]

I have several CAD designs I print out and use as paper patterns for sawing the basic outlines of the blade, handle and spring.

I've never made a template or a prototype for any knife. Each one is unique.

Yes, getting the rise and fall right is a chore.

Thanks for your input Don. I was just reading your Texas Toothpick build-along project from several years ago on another forum. Very instructive. Thanks again.